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http://dx.doi.org/10.3807/KJOP.2017.28.6.290

Testing of a Convex Aspheric Secondary Mirror for the Cassegrain Telescope  

Kim, Goeun (Science of Measurement, University of Science and Technology)
Rhee, Hyug-Gyo (Science of Measurement, University of Science and Technology)
Yang, Ho-Soon (Science of Measurement, University of Science and Technology)
Publication Information
Korean Journal of Optics and Photonics / v.28, no.6, 2017 , pp. 290-294 More about this Journal
Abstract
The Cassegrain telescope consists of a primary concave mirror and a secondary convex mirror. In the case of a secondary mirror, it is more difficult to test wavefront error than for a primary mirror, because it reflects the entire testing beam, as it is convex in shape. In this paper we tested the wavefront error of a complex aspheric convex secondary mirror by using the Simpson-Oland-Meckel Hindle test. To separate the systematic errors, such as fabrication error and alignment error of a meniscus lens, we adopted the QN absolute test (pixel-based absolute test using the quasi-Newton method) as well. Finally, we compared the measured result with that of an ASI (Aspheric Stitching Interferometer) made by the QED company, which resulted in an rms difference of only 2.5 nm, showing a similar shape of astigmatism aberration.
Keywords
Aspherics; Wavefront error; Error compensation; Testing;
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